Devices comprising two sound-generating means are known and widely used.
Spatial localization of sound has always been considered to be of paramount importance in audio reproduction devices. Contemporary sound reproduction devices are required to have at least stereo playback capabilities, and two or more loudspeakers are conventionally provided for such facilities. This usually results in devices with external loudspeakers separated from each other by a considerable distance and the associated footprint and wiring issues. However, this requires a space with enough distance between the loudspeakers, which is not always available and often also requires wiring. In many circumstances, more compact devices would be preferred. However, although such compact devices have been developed and sold, the stereo playback of these devices such as ‘ghettoblasters’ is not perceived as true stereo playback because the loudspeakers are spaced very close to each other. Some stereo-widening techniques such as Philips' “Incredible Surround” are known and overcome such limitations to some extent. However, such techniques may typically reduce the “sweet spot” (i.e. the area in which a good or acceptable stereo sound is produced), which sometimes becomes impractically small since consumers typically do not sit exactly in front of such a sound device. Furthermore, such techniques are usually complicated. Typically, compact devices for producing stereo sound have the drawback that, although they do provide stereo sound only in or near the sweet spot, the positions in which this is achieved is limited to usually a rather small area right in front of the device. For true stereo sound perception, it is highly preferred that the stereo sound perception remains when a listener walks around or, when more than one person is listening to the sound, all listeners are provided with substantially the same quality of sound. The stereo signal has a left and a right sound signal. The denotations “left” and “right” are understood to merely indicate one of the usual sub-signals of a stereo signal (wherein “stereo signal” may be any multi-channel signal). Unless specifically described otherwise, these denotations are not understood to be anything else but such a simple division of the stereo signal using common terms, and not an undue restriction. In a simple embodiment, however, “left” and “right” stand for the usual “left” and “right” stereo channels.
Thus there is a need for a device that is capable of giving a stereo sound sensation to the listener over a relatively large area while yet being a, preferably very, compact sound reproduction device.